Tablets used commonly as oral preparations are formed by using various additives such as diluents, binders, lubricants, disintegrators, etc. Depending on an active compound, some tablets are less stable to light during circulation and storage and these tablets are often provided with a coating film capable of exerting a light protecting effect by film coating. It is also a useful means to form a coating film in order to prevent bitterness of a drug. This coating film is generally composed of hydroxypropylmethylcellulose (HPMC) or hydroxypropylcellulose (HPC) as water-soluble coating film agents, polyethylene glycol (PEG) as plasticizers and titanium dioxide as light-protecting agents and, if necessary, iron sesquioxide such as colorants.